Abstract：The true stress-strain curve for ultra-high strength steel Q&P980 is obtained through cyclic loading of the ultra-high strength steel in terms of the number of cycles, cyclic position and anisotropy of the cyclic tensile test. The properties of the unloading ring were also analyzed to accurately characterize the mechanical properties. A metallographic microscope using X-ray diffraction (XRD) was then used to study the microstructural changes. The results show that increasing the deformation reduced the slope of the unloading and reloading curves. In addition, reducing the austenite content increased the springback strain, elongation and strength, which is called the transformation induced plasticity (TRIP) effect. For similar amounts of deformation, increasing the number of cycles did not increase the springback strain but reduce it when the cycle number increased to 10. The cyclic loading weakens the sheet anisotropy, but has little effect on the elastic modulus and springback.
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2018, Vol. 58 
